1. Field of the Invention
The present invention relates to a color ink jet recording apparatus for performing recording by ejecting a plurality of colors of inks from a recording head having a plurality of ejection orifices.
2. Related Background Art
A case will be examined in detail below wherein a mixed-color dot is formed by landing ink droplets of different colors. When the ink absorbing characteristics of a recording medium are improper in the vertical and horizontal directions, a post deposited ink is absorbed under a pre-deposited ink, and the landing diameter is increased on the surface of the recording medium. FIGS. 14A and 14B show a state wherein a post deposited Y ink spreads outwardly from a pre-deposited C ink. FIG. 14A shows a dot array observed from the recording surface of a recording medium, and FIG. 14B is a sectional view of one dot. When the state of such a solid G portion is enlarged to a visible level, a G portion (hatched portion) obtained by mixing C and Y colors is present inside the dots, and a Y portion (not pure Y, but Y slightly mixed with C, i.e., yellow-rich green; to be referred to as G(Y) hereinafter) spreads to surround the G portion, as shown in FIG. 15. In this case, since a serial printer is used, a carriage performs a line feed operation according to the recording width after the recording operation of each line, and then continues the recording operation of the next line. If a solid G portion having an area over several lines is recorded, each line corresponds to the solid G portion shown in FIG. 15. More specifically, a G(Y) portion spreads from the peripheral portion of the recorded portion of each line, and a connection section between two adjacent lines is connected by G(Y) portions. For this reason, although the inner portion of each line is recorded in G, a G(Y) portion becomes linearly conspicuous in the horizontal direction in the connection section between the adjacent lines. Thus, a whitish horizontal stripe is formed. This phenomenon is called "banding", and considerably deteriorates the image quality of a solid mixed-color portion.
As a recording mode for preventing this phenomenon, a thinning multi-pass recording method for recording thinned patterns of a connection section in a plurality of number of times of recording scan operations (described in, e.g., U.S. Pat. No. 4,967,203) is known. In the case of a 2-pass recording mode as an example of the multi-pass recording mode, some dots, e.g., dots thinned out in a checker pattern are recorded in the first-pass carriage scan operation, and a line feed operation is performed by a line space 1/2 a normal space. Thereafter, dots thinned out in a reverse checker pattern for compensating for the former dot pattern are recorded in the second-pass carriage scan operation (to be referred to as a thinning multi-pass 1/2 line-space method hereinafter). According to the thinning multi-pass 1/2 line-space method, a stripe pattern in a connection section is not so conspicuous as compared to a normal 1-pass recording method.
However, this method is insufficient, and a white or black stripe pattern may often be formed in a connection section between adjacent lines, thus posing a serious problem upon formation of an image in a serial color ink jet recording apparatus.